1. Field of the Invention
The present invention relates to an engine starting device including a self-starter mechanism for starting an engine.
2. Description of the Related Art
Some of engines used in agricultural machinery or snowplows include an engine starting device equipped with a two-way or dual starting system having a self-starter mechanism and a recoil starter mechanism.
The self-starter mechanism includes a self-starting motor adapted to be driven by a starter button and is constructed to transmit rotation of the self-starting motor to a crankshaft of the engine for rotating the crankshaft until the engine fires and continues to run on its own power. The self-starter mechanism is easy to handle because the engine can be driven or started by merely depressing the starter button.
Since the agricultural machinery and snowplows are seasonal equipment used in a particular season of the years it occurs likely that the self-starting motor cannot start the engine due to a battery having being discharged during a non-use period of the equipment.
The recoil starter mechanism includes a starting rope adapted to be pulled by the operator to rotate a pulley and is constructed to transmit rotation of the pulley to the crankshaft for starting the engine. The recoil starter mechanism arranged to manually rotate the crankshaft is advantageous in that the engine can be started even when the battery is dead.
One example of the engine starting devices having such two-way starting system is disclosed in Japanese Patent Laid-open Publication No. HEI-2-108854.
The disclosed engine starting device is re-illustrated here in FIG. 19A. As shown, the engine starting device generally denoted by 150 is activated to start an engine 168 by using a self-starter mechanism.
A self-starting motor 151 of the engine starting device 150 is driven to rotate an output shaft 152 whereupon rotation of the output shaft 152 is transmitted through a first gear 153 and a second gear 154 to a first intermediate shaft 155. Subsequently, rotation of the first intermediate shaft 155 is transmitted through a third gear 156 and a fourth gear 157 to a second intermediate shaft 158. Then, rotation of the second intermediate shaft 158 is transmitted through a first one-way clutch 160 and a fifth gear 163 to a sixth gear 164. Rotation of the sixth gear 164 is transmitted via a third one-way clutch 165 to a crankshaft 166 of the engine 168 whereby the crankshaft 166 is rotated until the engine 168 fires and continue to run on its own power. In this instance, a second one-way clutch 170 is in the disengaged or released position so that rotation of the sixth gear 164 is not transmitted to a pulley 171.
As diagrammatically shown in FIG. 19B, the first one-way clutch 160 is of the type generally known in the art and includes an inner race 160a mounted to the second intermediate shaft 158, an outer race 160b concentric to the inner race 160a, a plurality of substantially triangular or wedge-like recesses 160c formed in an outer circumferential surface of the inner race 160a such that respective wedge-shaped portions of the recesses 160c are directed in the same circumferential direction of the inner race 160a, a plurality of balls 160d each received in one of the wedge-like recesses 160c, and a plurality of springs 160e each disposed in one of the wedge-like recesses 160c and urging the associated ball 160d toward the wedge-shaped portion of each recess 160c. 
When the second intermediate shaft 158 rotates clockwise as indicated by the arrow x shown in FIG. 19B, the inner race 160a rotates in unison with the second intermediate shaft 158. Rotation of the inner race 160a in the direction of the arrow x wedges balls 160d between an inner circumferential surface of the outer race 160b and the recessed outer circumferential surface of the inner race 160a, whereby the inner race 160a and the outer race 160b are connected together (that is, the one-way clutch 160 is engaged). Thus, rotation of the second intermediate shaft 158 is transmitted to the outer race 160b to thereby rotate the fifth gear 163 in the direction of the arrow x. By thus rotating the fifth gear 163, the crankshaft 166 is rotated to start the engine 168, as described above with reference to FIG. 19A.
When the engine 168 is to be started by using the recoil starter mechanism, the operator while gripping a grip 174 pulls a starting rope 175 as indicated by the arrow shown in FIG. 20A to thereby rotate a pulley 171. Rotation of the pulley 171 is transmitted through the second one-way clutch 170 and the third one-way clutch 165 to the crankshaft 166 whereby the crankshaft 166 is rotated to start the engine 168.
In this instance, the fifth gear 163 is rotated in the direction of the arrow x, and rotation of the fifth gear 163 is transmitted to the first one-way clutch 160.
Rotation of the fifth gear 163 in the direction of the arrow x causes the outer race 160b of the one-way clutch 160 to rotate in the same direction x as the fifth gear 163. Sine the second intermediate shaft 158 and the inner race 160a are held stationary, rotation of the outer race 160b in the direction of the arrow x releases the balls 160d from wedging engagement between the inner circumferential surface of the outer race 160b and the recessed outer circumferential surface of the inner race 160a, as shown in FIG. 20B. Thus, the inner race 160a and the outer race 160b are disengaged from each other (i.e., the one-way clutch 160 is released). As a result, rotation of the fifth gear 163 is not transmitted to the self-starting motor 151.
However, it may occur that when the engine 168 is about to stop, a piston (not shown) of the engine 168 cannot move past the upper dead center, causing the crankshaft 166 to rotate in the reverse direction, as indicated by the arrow shown in FIG. 21A. Reverse rotation of the crankshaft 166 is transmitted to the first one-way clutch 160 successively through the third one-way clutch 165, sixth gear 164 and fifth gear 163.
As the fifth gear 163 is thus rotated in the direction of the arrow y, the outer race 160b of the first one-way clutch 160 rotates in the direction of the arrow y, as shown in FIG. 21B. Rotation of the outer race 160b in the direction of the arrow y wedges the balls 160d between the inner circumferential surface of the outer race 160b and the recessed outer circumferential surface of the inner race 160a, whereby the inner race 160a and the outer race 160b are connected together (i.e., the one-way clutch 160 is engaged). As a result, the inner race 160a rotates in unison with the outer race 160b in the direction of the arrow y.
This will cause that rotation of the inner race 160a and second intermediate shaft 155 is transmitted to the output shaft 152 successively through the fourth gear 157, third gear 156, first intermediate shaft 155, second gear 154 and first gear 153. This means that the self-starting motor 161 is rotated in the reverse direction. To deal with this problem, the self-starting motor 161 requires strengthening or reinforcement of structural components which will induce additional cost and labor.
In the case where the engine is installed in a snowplow, it may occur that the self-starting motor 161 is driven before a lot of snow deposited on a snowplow attachment is removed, resulting in a failure to rotate the crankshaft against a heavy load exerted on the snowplow attachment. In this instance, the self-starting motor 161 is overloaded. To deal with this problem, the self-starting motor components require extensive strengthening.
It is accordingly an object of the present invention to provide an engine starting device which is capable of preventing a self-starting motor from being rotated in the reverse direction and also from being overloaded.
Another object of the present invention is to provide an engine starting device including a highly durable one-way clutch.
A further object of the present invention is to provide an engine starting device which is capable of suppressing operation noise when a one-way clutch is allowed to free wheel after a self-starting motor is shut off.
According to the present invention, there is provided an engine starting device for rotating a crankshaft of an engine to start the engine. The engine starting device includes a self-starting motor drivable to rotate the crankshaft of the engine, and a one-way clutch disposed between the self-starting motor and the crankshaft of the engine and operable to transmit rotary motion of the self-starting motor to the crankshaft. The one-way clutch is comprised of an inner race operatively connected to an output shaft of the self-starting motor for co-rotation therewith, an outer race concentric to the inner race and operatively connected to the crankshaft, a plurality of ratchet pawls pivotally connected to the inner race for pivotal movement within an annular space defined between the inner race and the outer race, and a plurality of springs acting between the inner race and the ratchet pawls and urging the ratchet pawls against the inner race to thereby keep the ratchet pawls out of contact with the outer race. The one-way clutch is arranged such that when the speed of rotation of the inner race while being rotated by the self-starting motor goes up to a predetermined value, the ratchet pawls are caused to swing in a radial outward direction under the action of centrifugal force against the force of the springs and become engaged by the outer race to thereby engage the one-way clutch.
When the crankshaft is reversed, reverse rotation of the crankshaft is transmitted to the outer race. In this instance, however, since the ratchet pawls are normally urged against the inner race and hence held out of contact with the outer race, transmission of reverse rotation of the crankshaft to the inner race does not take place. The self-starting motor can thus be protected against destructive overload.
In one preferred form, the outer race has a plurality of ratchet teeth formed on an inner circumferential surface of the outer race. The ratchet teeth are lockingly engageable with respective free ends of the ratchet pawls.
In order to facilitate smooth engaging operation of the one-way clutch, it is preferable that the number of the ratchet teeth is at least equal to the number of the ratchet pawls. The number of the ratchet teeth may be an integral multiple of the number of the ratchet pawls.
The ratchet pawls preferably have a pivot shaft rotatably supported at opposite ends thereof to the inner race so as to ensure reliable operation of the ratchet pawls. In one preferred form, one end of the pivot shaft is rotatably received in an axial hole formed in the inner race and the other end of the pivot shaft is rotatably received in a hole formed in a support plate attached to the inner race.
The engine starting device may further include a torque limiter assembled on the output shaft of the self-starting motor for protecting the self-starting motor against overload. The torque limiter is designed to automatically slip at a predetermined torque.
In one preferred form, the torque limiter is comprised of an inner race rotatably mounted on the output shaft of the self-starting motor, a plurality of lock pins partly received in a plurality of axial grooves, respectively, formed in an outer circumferential surface of the inner race, a bias member for urging the lock pins into the axial grooves, and an outer race concentric to the inner race and firmly connected to the output shaft of the self-starting motor. The outer race has a plurality of axial grooves formed in an inner circumferential surface thereof for receiving respectively therein at least a part of the locking pins. The axial grooves of the outer race have a depth large enough to fully accommodate therein the lock pins. It is preferable that the axial grooves of the inner race have a generally V-shaped cross section, and the axial grooves of the outer race have a generally U-shaped cross section.
The bias member of the torque limiter is a resilient ring wound around the lock pins and resiliently urging the lock pins in a radial inward direction. The resilient ring may be a coiled ring spring. The lock pins preferably have a circumferentially grooved central portion in which the resilient ring is partly received. The outer race may further have a circumferential groove formed in the inner circumferential surface thereof for receiving therein part of the resilient ring.
In one preferred form, the engine starting device further include a motor drive circuit for driving the self-starting motor. The motor drive circuit includes a start switch adapted to be turned on and off to electrically connect and disconnect the self-starting motor with a source of electric power for energizing and de-energizing the self-starting motor, and a short circuit formed across terminals of the self-starting motor when the start switch is turned off.
By thus short-circuiting the terminals of the self-starting motor when the start-switch is turned off to shut off the self-starting motor, a dynamic braking system is created in which the retarding force is supplied by the self-starting motor itself that originally was the driving motor. Thus, the self-starting motor can be stopped suddenly by the effect of a braking action resulting from a counter electromotive force. Since the self-starting motor comes to a sudden stop, the centrifugal force acting on the ratchet pawls is killed suddenly. Thus, the ratchet pawls are allowed to rapidly return to their original released position under the force of the springs. With this rapid returning of the ratchet pawls, the one-way clutch can be disengaged or released without involving interference or collision between the ratchet teeth and the ratchet pawls which would otherwise result in the generation of striking noise and vibrations. Thus, the engine starting device including the motor drive circuit is able to operate silently.
The source of electric power may be an a.c. power source. The self-starting motor may be a d.c. motor in which instance the motor control circuit further includes a power circuit for converting a.c. voltage to d.c. voltage. Preferably, the engine starting device is incorporated in an engine installed in an engine-driven snowplow.
The above and other objects, features and advantages of the present invention will becomes apparent to these versed in the art upon making reference to the following detailed description and accompanying sheets of drawings in which a certain preferred structural embodiment incorporating the principle of the present invention are shown by way of illustrative example.